1. Field of the Invention
The present invention relates to a switching power supply unit in which a switched output obtained by switching a DC input voltage is taken out in an output winding of a power converting transformer.
2. Description of the Related Art
Hitherto, various types of DC-DC converters have been proposed as a switching power supply unit and provided for practical use. Many of them are of a type in which a DC input voltage is switched with a switching operation by a switching circuit (inverter circuit) that is connected to a primary winding of a power converting transformer (transformer device), and the switched output (inverter output) is taken out in a secondary winding of the power converting transformer (transformer). The voltage appearing in the secondary winding in accordance with the switching operation of the switching circuit is rectified by a rectifier circuit, then is converted into a DC current by a smoothing circuit and outputted.
In related arts, this sort of switching power supply unit employs as a rectifier circuit a circuit of a center tap type (refer to Japanese Patent Publication Application No. 2007-60890 for example) and a circuit of a current doubler type (for example, refer to U.S. Pat. No. 4,899,271 and Japanese Patent Publication Application No. 1999-187657).